“Conical”-type rotary valves have been in use for over 40 years in chromatographic applications and various other sampling systems. Early conical valve designs include “plug” or “stopcock” valves, such as for example shown in U.S. Pat. No. 2,830,738 (Sorg et al); U.S. Pat. No. 2,211,627 (Morgan); U.S. Pat. No. 2,972,888 (Lamkin); U.S. Pat. No. 3,116,642 (Weir); U.S. Pat. No. 3,475,950 (Ferrin); U.S. Pat. No. 3,683,701 (Gunther et al); and U.S. Pat. No. 4,133,640 (Clinton et al).
Typically, a rotary valve includes a stator having a plurality of fluid-open ports therein opening on its inner surface, and a rotor coaxially extending within the stator and rotatable with respect to their common axis. The rotor has channels or grooves opening on its outer surface, disposed so that rotating the rotor to predetermined angular positions will provide fluid communication between different ports of the stator through the channels or grooves of the rotor.
Referring to FIGS. 1A and 1B (PRIOR ART), there is shown an exploded view of a conventional conical rotary valve 10. The valve 10 includes a valve body 12 acting as a stator and defining a cavity 14 in which the rotor 16 is received. As mentioned above, the stator 12 has fluid-open ports (not shown) opening on the inside surface of the cavity 14, and the rotor has grooves 18 on its surface for providing fluid communication between the ports.
Actuating means are generally provided to control the rotation of the rotor 16 about an axis of rotation 17 between the desired angular positions. For example, a valve 10 may be coupled to an electric or pneumatic rotary actuator 11, as shown in FIGS. 2A and 2B (PRIOR ART). The valve 10 may also be coupled to a linear actuator 13, as shown in FIGS. 3A and 3B (PRIOR ART), or simply actuated manually through a handle.
Such valves 10 are typically provided with a drive adaptor 20 which engages the rotor 16 and transmits a rotational actuating force 19 thereto. Typically, the drive adaptor 20 comprises a body 21 which engages the rotor 16 and a transverse actuating pin 22 which extends therefrom. In the exemplary prior art embodiment illustrated in FIGS. 2A and 2B, the rotational actuating force 19 is transferred from the actuator 11 or 13 to the pin 22 via a drive coupling 27 which extends concentrically around the body 21 and receives the pin 22 in opposed slots 29. The actuating force is therefore transferred from the actuator 11 or 13 to the pin 22 via the drive coupling 27, and from the drive adaptor 20 to the rotor 16.
On one side of the drive coupling 27, the pin 22 extends beyond the slot 29 and a stopper 24 is provided on the stator 12 so as to limit the course of the pin 22, and thereby the rotation of the rotor 16. The rotation of the rotor 16 can be limited to a quarter turn, for example, or other appropriate traveling stroke.
Conical rotary valves often present cross-contamination or inboard/outboard leaks which are unacceptable for chromatographic applications. There is therefore a need for an improved conical rotary valve for chromatographic applications which alleviates at least some of these problems.